Mosquito-borne infectious diseases are an increasing global threat to humans. Blood-feeding mosquitoes transmit many of the world's deadliest diseases. Such diseases have resurged in developing countries and are also emerging as clear threats for epidemic outbreaks in developed countries. Numerous factors contribute to the current inability to prevent or control these diseases, including poor progress in vaccine development, the appearance of insecticide resistance in mosquito populations, the emergence of drug resistance in parasite populations, a general lack of support in many developing countries for mosquito control programs, and increased global travel. The mosquito genome projects have stimulated increased interest in the potential for arthropod-borne disease control by genetic manipulation of vector insects. Targets of particular interest include genes that regulate development. Analysis of genes that regulate mosquito nervous system development will lead to a better understanding of the developmental basis of motor function, sensory processing, and behavior, key aspects of mosquito host location. Furthermore, analysis of the development of mosquito salivary glands, which are essential for the spread of infection, could lead to creation of additional means of controlling mosquitoes. However, extremely little is known about the genetic regulation of these or other tissues during mosquito development. In recent years, evolutionary developmental biologists have applied knowledge of developmental genetics in Drosophila melanogaster, a genetically tractable model organism, to better understand development of other arthropods. Analysis of axon guidance molecules such as Netrins and Semaphorins in Drosophila indicate that these proteins regulate numerous developmental processes during fly development, including embryonic axon guidance, olfactory neural guidance, and salivary gland development. Preliminary data support the hypothesis that the roles of these genes are conserved in mosquitoes. Analysis of the functions of axon guidance genes in mosquitoes could therefore promote a better understanding of mosquito nervous system and salivary gland development. The specific aims of this investigation are to characterize the function of several axon guidance genes, including Netrin and its DCC receptor, and Semaphorin1a and its PlexinA receptor during mosquito development. These studies will include the yellow and dengue fever virus vector Aedes aegypti, as well as the malaria vector Anopheles gambiae. Methods that will be employed to test the hypothesis that axon guidance gene function is conserved in mosquitoes include gene and protein expression assays, as well as genetic knock-down strategies (RNA inhibition/morpholinos). Detailed analysis of the function of developmental regulatory genes and selective inhibition of such genes in mosquitoes is a requisite step toward attaining the long-term goals of this research program, which are to selectively target mosquito developmental genes in an effort to control mosquito-borne infectious diseases. PUBLIC HEALTH RELEVANCE: Although very little is known about the genes that regulate vector mosquito development, genetic analysis of mosquito development can reveal new targets for mosquito-control agents. The proposed research aims to analyze the function of several developmental regulatory genes in the dengue and yellow fever virus vector Aedes aegypti and the malaria vector Anopheles gambiae through analysis of gene expression and RNA inhibition studies. Results obtained in these studies will likely be applicable to other vector mosquitoes.